Adjustable modulation coding scheme to increase video stream robustness

ABSTRACT

Systems, apparatuses, and methods for utilizing different modulation coding schemes (MCSs) for different components of a video stream are disclosed. A system includes a transmitter sending a video stream over a wireless link to a receiver. The transmitter splits the video stream into low, medium, and high quality components, and then the transmitter modulates the different components using different MCS&#39;s. For example, the transmitter modulates the low quality component using a lower, robust MCS level to increase the likelihood that this component is received. Also, the medium quality component is modulated using a medium MCS level and the high frequency component is modulated using a higher MCS level. If only the low quality component is received by the receiver, then the receiver reconstructs and displays a low quality video frame from this component, which avoids a glitch in the display of the video stream.

BACKGROUND Description of the Related Art

A wireless communication link can be used to send a video stream from acomputer (or other device) to a virtual reality (VR) headset (or headmounted display (HMD). Transmitting the VR video stream wirelesslyeliminates the need for a cable connection between the computer and theuser wearing the HMD, thus allowing for unrestricted movement by theuser. A traditional cable connection between a computer and HMDtypically includes one or more data cables and one or more power cables.Allowing the user to move around without a cable tether and withouthaving to be cognizant of avoiding the cable creates a more immersive VRsystem. Sending the VR video stream wirelessly also allows the VR systemto be utilized in a wider range of applications than previouslypossible.

However, a VR application is a low latency application and typicallyonly buffers a small amount of video data. For example, when the usermoves their head, this is detected by the HMD or console, and then thesubsequently rendered video frames are updated to reflect the newviewing position of the user. Additionally, changing conditions of thelink can affect video quality. When the link deteriorates and video datais lost or corrupted, this can result in a poor user viewing experience.Accordingly, improved techniques for wireless streaming of data aredesired.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the methods and mechanisms described herein may bebetter understood by referring to the following description inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of one embodiment of a system.

FIG. 2 is a block diagram of one embodiment of a wireless virtualreality (VR) system.

FIG. 3 is a diagram of one embodiment of transmit and receivebeamforming sectors.

FIG. 4 is a diagram of packets for use in wireless communication inaccordance with various embodiments.

FIG. 5 is a block diagram of one embodiment of transmitter logic.

FIG. 6 illustrates tables for mapping components to MCS levels based onlink quality in accordance with one embodiment.

FIG. 7 is a generalized flow diagram illustrating one embodiment of amethod for splitting a video stream into multiple components and usingdifferent modulation for the different components.

FIG. 8 is a generalized flow diagram illustrating another embodiment ofa method for utilizing different retry policies for different componentsof a video stream.

FIG. 9 is a generalized flow diagram illustrating one embodiment of amethod for determining a MCS level for a low quality component based onlink quality.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following description, numerous specific details are set forth toprovide a thorough understanding of the methods and mechanisms presentedherein. However, one having ordinary skill in the art should recognizethat the various embodiments may be practiced without these specificdetails. In some instances, well-known structures, components, signals,computer program instructions, and techniques have not been shown indetail to avoid obscuring the approaches described herein. It will beappreciated that for simplicity and clarity of illustration, elementsshown in the figures have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements may be exaggeratedrelative to other elements.

Various systems, apparatuses, methods, and computer-readable mediums forutilizing different modulation coding schemes (MCSs) for differentcomponents of a video stream are disclosed herein. In one embodiment, awireless communication system includes a transmitter and a receivercommunicating over a wireless link. In one embodiment, the transmitteris configured to encode a video stream and wirelessly transmit theencoded video stream to the receiver. In one embodiment, the videostream is part of a virtual reality (VR) rendered environment.

In one embodiment, the transmitter splits the video stream into aplurality of components and then the transmitter modulates the differentcomponents using different MCS levels. The technique utilized by thetransmitter for splitting the video stream into a plurality ofcomponents can vary from embodiment to embodiment. In one embodiment,the transmitter utilizes successive compression to split the videostream into a lower quality substream and one or more successivelyhigher quality substreams. The number of higher quality sub streams canvary according to the embodiment. Each higher quality substream willrequire the successful reception of all of the lower quality substreamsto be successfully decoded. The higher quality substreams areeffectively incremental enhancements to the lower quality substreams.The transmitter modulates the low quality substream using a relativelylow MCS level. This relatively low MCS level is a robust MCS whichincreases the likelihood that the low quality substream is received bythe receiver. If only the low quality substream is received by thereceiver, then the receiver is able to reconstruct a video frame fromthis substream only, which avoids a glitch in the display of the videosequence. The successively higher quality substreams are modulated withsuccessively higher MCS levels.

In another embodiment, the transmitter splits the video stream into aplurality of components based on frequency information. In otherembodiments, the transmitter can utilize other techniques to split thevideo stream into a plurality of components. It is noted that a“component” of a video stream can also be referred to as a “substream”or “subset bitstream” herein. In one embodiment, the transmitter splitsthe video stream into a low frequency component, a medium frequencycomponent, and a high frequency component. In this embodiment, thetransmitter modulates the low frequency component using a relatively lowMCS level. This relatively low MCS level is a robust MCS which increasesthe likelihood that the low frequency component is received by thereceiver. Also, in this embodiment, the medium frequency component ismodulated using a relatively average MCS level and the high frequencycomponent is modulated using a relatively high MCS level. If only thelow frequency component is received by the receiver, then the receiverreconstructs a low frequency video frame from this component, whichavoids a glitch in the display of the video sequence.

Referring now to FIG. 1 , a block diagram of one embodiment of a system100 is shown. System 100 includes at least a first communications device(e.g., transmitter 105) and a second communications device (e.g.,receiver 110) operable to communicate with each other wirelessly. It isnoted that transmitter 105 and receiver 110 can also be referred to astransceivers. In one embodiment, transmitter 105 and receiver 110communicate wirelessly over the unlicensed 60 Gigahertz (GHz) frequencyband. For example, transmitter 105 and receiver 110 can communicate inaccordance with the Institute of Electrical and Electronics Engineers(IEEE) 802.11ad standard (i.e., WiGig). In other embodiments,transmitter 105 and receiver 110 can communicate wirelessly over otherfrequency bands and/or by complying with other wireless communicationprotocols, whether according to a standard or otherwise. For example,other wireless communication protocols that can be used include, but arenot limited to, Bluetooth®, protocols utilized with various wirelesslocal area networks (WLANs), WLANs based on the Institute of Electricaland Electronics Engineers (IEEE) 802.11 standards (i.e., WiFi), mobiletelecommunications standards (e.g., CDMA, LTE, GSM, WiMAX), etc.

Wireless communication devices that operate within extremely highfrequency (EHF) bands, such as the 60 GHz frequency band, are able totransmit and receive signals using relatively small antennas. However,such signals are subject to high atmospheric attenuation when comparedto transmissions over lower frequency bands. In order to reduce theimpact of such attenuation and boost communication range, EHF devicestypically incorporate beamforming technology. For example, the IEEE802.11ad specification details a beamforming training procedure, alsoreferred to as sector-level sweep (SLS), during which a wireless stationtests and negotiates the best transmit and/or receive antennacombinations with a remote station. In various embodiments, transmitter105 and receiver 110 are configured to perform periodic beamformingtraining procedures to determine the optimal transmit and receiveantenna combinations for wireless data transmission.

In one embodiment, transmitter 105 and receiver 110 have directionaltransmission and reception capabilities, and the exchange ofcommunications over the link utilizes directional transmission andreception. Each directional transmission is a transmission that isbeamformed so as to be directed towards a selected transmit sector ofantenna 140. Similarly, directional reception is performed using antennasettings optimized for receiving incoming transmissions from a selectedreceive sector of antenna 160. The link quality can vary depending onthe transmit sectors selected for transmissions and the receive sectorsselected for receptions. The transmit sectors and receive sectors whichare selected are determined by system 100 performing a beamformingtraining procedure.

Transmitter 105 and receiver 110 are representative of any type ofcommunication devices and/or computing devices. For example, in variousembodiments, transmitter 105 and/or receiver 110 can be a mobile phone,tablet, computer, server, head-mounted display (HMD), television,another type of display, router, or other types of computing orcommunication devices. In one embodiment, system 100 executes a virtualreality (VR) application for wirelessly transmitting frames of arendered virtual environment from transmitter 105 to receiver 110. Inother embodiments, other types of applications can be implemented bysystem 100 that take advantage of the methods and mechanisms describedherein.

In one embodiment, transmitter 105 includes at least radio frequency(RF) transceiver module 125, processor 130, memory 135, and antenna 140.RF transceiver module 125 is configured to transmit and receive RFsignals. In one embodiment, RF transceiver module 125 is a mm-wavetransceiver module operable to wirelessly transmit and receive signalsover one or more channels in the 60 GHz band. RF transceiver module 125converts baseband signals into RF signals for wireless transmission, andRF transceiver module 125 converts RF signals into baseband signals forthe extraction of data by transmitter 105. It is noted that RFtransceiver module 125 is shown as a single unit for illustrativepurposes. It should be understood that RF transceiver module 125 can beimplemented with any number of different units (e.g., chips) dependingon the embodiment. Similarly, processor 130 and memory 135 arerepresentative of any number and type of processors and memory devices,respectively, that can be implemented as part of transmitter 105.

Transmitter 105 also includes antenna 140 for transmitting and receivingRF signals. Antenna 140 represents one or more antennas, such as aphased array, a single element antenna, a set of switched beam antennas,etc., that can be configured to change the directionality of thetransmission and reception of radio signals. As an example, antenna 140includes one or more antenna arrays, where the amplitude or phase foreach antenna within an antenna array can be configured independently ofother antennas within the array. Although antenna 140 is shown as beingexternal to transmitter 105, it should be understood that antenna 140can be included internally within transmitter 105 in variousembodiments. Additionally, it should be understood that transmitter 105can also include any number of other components which are not shown toavoid obscuring the figure. Similar to transmitter 105, the componentsimplemented within receiver 110 include at least RF transceiver module145, processor 150, memory 155, and antenna 160, which are analogous tothe components described above for transmitter 105. It should beunderstood that receiver 110 can also include or be coupled to othercomponents (e.g., a display).

In various embodiments, the link between transmitter 105 and receiver110 has capacity characteristics that fluctuate with variations in theenvironment. To combat the fluctuating capacity characteristics of thelink, transmitter 105 is configured to separate a data stream intomultiple components and transmit each component using a differentmodulation coding scheme (MCS). For example, in one embodiment, the datastream is encoded into a high priority component and one or more lowerpriority components. The high priority component is the component whichtransmitter 105 modulates with a robust MCS to increase the likelihoodthat this component is received by receiver 110.

In one embodiment, the data stream is a video stream, and the videostream is split into a plurality of substreams using successivecompression. In one embodiment, the lowest quality substream (i.e., highpriority substream) is modulated using a robust MCS level (i.e., low MCSlevel) to increase the likelihood that the lowest quality substream isreceived by receiver 110. The other substreams of higher quality aresent to receiver 110 using relatively less robust MCS levels (i.e.,relatively high MCS level). Due to robust coding, receiver 110 likelyreceives the lowest quality substream in the worst case, and receiver110 is able to reconstruct a lower quality (i.e., lower resolution)video frame from this substream, which prevents a glitch in the userviewing experience.

In one embodiment, the data stream is a video stream, and the videostream is split into a plurality of substreams based on frequencyinformation. For example, in one embodiment, the video stream is splitinto a low frequency version of the video (i.e., the high prioritystream), a medium frequency version of the video (i.e., the mediumpriority stream), and a high frequency version of the video (i.e., thelow priority stream). In some cases, it is preferable that at least thelow frequency version of the video is received by receiver 110. In thisway, receiver 110 can avoid glitches when displaying the received videoeven if the high and medium frequency versions of the video are notreceived. The scheme of splitting the video stream into separatecomponents which are modulated differently allows for robustcommunication over a lossy channel between transmitter 105 and receiver110.

The high priority component can also be referred to as a low frequencycomponent, low quality component, or low bitrate component. Similarly,the medium priority component can also be referred to as a mediumfrequency component, medium quality component, or medium bitratecomponent. Also, the low priority component can also be referred to as ahigh frequency component, high quality component, or high bitratecomponent. It is noted that the term “component” can also be usedinterchangeably with “stream”, “elements”, or “subset bitstream” inrelation to the above terms.

In one embodiment, pre-compression data is processed multiple times toproduce separate lower quality/bitrate and higher quality/bitratestreams, with the higher-quality stream being a derivation of thelower-quality stream. The process is a successive approximation which isnot limited to two streams of lower/higher-quality but can also be usedto generated N streams of different qualities/bitrates. In oneembodiment, the video stream is processed with a first compression ratioto produce a lower bitrate stream. In this embodiment, a higher bitratestream is generated from the delta of the lower bitrate stream and theoriginal stream at a second lower compression ratio. In anotherembodiment, alternatively coded information such as motion vectors canbe sent in a lower-bitrate, higher-resilience stream.

The lower quality stream can be modulated with a relatively lower MCSlevel to increase the probability that the lower quality stream isreceived by receiver 110. The medium quality stream can be modulatedwith a medium MCS level and the higher quality stream can be modulatedwith a relatively higher MCS level. It is noted that a “MCS level” canalso be referred to as a “MCS index”. In one embodiment, a lower MCSlevel, which has a higher reliability, would transport thelower-frequency, lower-quality information with the MCS level fixedbased up on the targeted reliability and expected bandwidth requirementof the data. In this embodiment, the higher-frequency, higher-qualityinformation is transmitted on a MCS level based upon the compressionsettings which are selected to fit the available bandwidth and/or basedupon the capacity of the established link.

In one embodiment, with the lower-frequency, lower-quality stream andthe higher-frequency, higher-quality stream having independentcompression settings, each stream can be mapped to a different MCSlevel. In this embodiment, the MCS level for a given stream is selectedbased on risk, resilience, and quality factors where higher resiliencyis achieved with a lower MCS level but with a lower quality. Also, lowerresiliency and higher quality is achieved with a higher MCS level. Bysplitting the video stream into lower-frequency and higher-frequencystreams, a higher level of fallback quality is achieved.

Turning now to FIG. 2 , a block diagram of one embodiment of a wirelessvirtual reality (VR) system 200 is shown. System 200 includes at leastcomputer 210 and head-mounted display (HMD) 220. Computer 210 isrepresentative of any type of computing device which includes one ormore processors, memory devices, input/output (I/O) devices, RFcomponents, antennas, and other components indicative of a personalcomputer or other computing device. In other embodiments, othercomputing devices, besides a personal computer, can be utilized to sendvideo data wirelessly to head-mounted display (HMD) 220. For example,computer 210 can be a gaming console, smart phone, set top box,television set, video streaming device, wearable device, a component ofa theme park amusement ride, or otherwise. Also, in other embodiments,HMD 220 can be a computer, desktop, television or other device used as areceiver connected to a HMD or other type of display.

Computer 210 and HMD 220 each include circuitry and/or components tocommunicate wirelessly. It is noted that while computer 210 is shown ashaving an external antenna, this is shown merely to illustrate that thevideo data is being sent wirelessly. It should be understood thatcomputer 210 can have an antenna which is internal to the external caseof computer 210. Additionally, while computer 210 can be powered using awired power connection, HMD 220 is typically battery powered.Alternatively, computer 210 can be a laptop computer powered by abattery.

In one embodiment, computer 210 includes circuitry configured todynamically render a representation of a VR environment to be presentedto a user wearing HMD 220. For example, in one embodiment, computer 210includes one or more graphics processing units (GPUs) to render a VRenvironment. In other embodiments, computer 210 can include other typesof processors, including a central processing unit (CPU), applicationspecific integrated circuit (ASIC), field programmable gate array(FPGA), digital signal processor (DSP), or other processor types. HMD220 includes circuitry to receive and decode a compressed bit streamsent by computer 210 to generate frames of the rendered VR environment.HMD 220 then drives the generated frames to the display integratedwithin HMD 220.

In one embodiment, after rendering a frame of a virtual environmentvideo stream, computer 210 splits the rendered frame into N componentsand then sends the N components wirelessly to HMD 220. Each of the Ncomponents represents the video at a different frequency, bitrate,quality, and/or resolution, and computer 210 uses a different modulationto modulate each of the different components. In one embodiment, thecomponents are transmitted as physical layer convergence procedure(PLCP) protocol data units (PPDUs). In some embodiments, the threecomponents are combined in an aggregate PPDU (A-PPDU). A PPDU beginswith a short training field (STF), followed by a header and then apayload. Typically, there is an inter frame space (IFS) field in betweenseparate payloads. In one embodiment, each of the components isencapsulated into a different payload of an A-PPDU, and then the A-PPDUis sent from computer 210 to HMD 220.

In one embodiment, the goal is to send the component representing thelow frequency/bitrate/quality video using a more reliable modulationcoding scheme (MCS) to increase the likelihood that at least someversion of the video frame can be displayed. For example, a low MCSlevel such as MCS 1 using binary phase shift keying (BPSK) encodes asingle bit per symbol and is a robust modulation since it takes a higheramount of noise or distortion to make the demodulator reach an incorrectdecision as compared to a less reliable MCS. MCS 1 offers protectionagainst channel errors at the expense of a lower transmission rate.Accordingly, in one embodiment, the low frequency component is modulatedusing BPSK modulation, the medium frequency component is modulated usingquadrature phase shift keying (QPSK) modulation, and a third, highfrequency component is modulated using 16 quadrature amplitudemodulation (QAM). In other embodiments, the components of the video canbe modulated using other MCS levels.

Referring now to FIG. 3 , a diagram depicting transmit and receivebeamforming sectors is shown. In one embodiment, transmitter 310 isconfigured to perform each of its directional transmissions towards arespective transmit sector selected from among a plurality of transmitsectors 315A-N. Transmit sectors 315A-N are representative of any numberof transmit sectors, with the number varying from embodiment toembodiment. Receiver 320 is configured to perform each of itsdirectional receptions from a respective receive sector selected fromamong a plurality of receive sectors 325A-N, which are representative ofany number of receive sectors.

When communicating with receiver 320, transceiver 310 directionallytransmits RF signals toward a selected one of transmit sectors 315A-N.If transceiver 310 transmits signals toward transmit sectors in adirection away from receiver 320, the energy levels of signals receivedby receiver 320 will be low, preventing receiver 320 from successfullyreceiving the signals. Otherwise, if transmitter 310 transmits signalsto a transmit sector oriented toward receiver 320, signals will arriveat receiver 320 with high levels of energy. For example, if receiver 320is monitoring receive sector 325A or 325B for incoming transmissions atthe same time that a signal arrives from transmitter 310 with highlevels of energy, receiver 320 will receive the signal with a high levelof power, enabling receiver 320 to successfully extract the data fromthe signal.

During beamforming training, transmitter 310 and receiver 320 each cyclethrough the different sectors to determine the best configuration fortransmitting data from transmitter 310 to receiver 320. If one or bothof transmitter 310 and receiver 320 are mobile, then the best sectorsfor transmitting data can change over time. Accordingly, transmitter 310and receiver 320 can repeat the beamforming training procedure atperiodic intervals to determine if an alternate configuration wouldresult in a better connection.

Transmitter 310 and receiver 320 are configured to reinitiate thebeamforming training procedure periodically in order to determinewhether link quality can be improved by using different beamformingparameters. In one embodiment, transmitter 310 and receiver 320determine whether to initiate a beamforming training procedure based ona signal-to-noise ratio (SNR) measurement of a received signal overbeamformed links, based on a packet reception rate, and/or based onother factors. For example, if the SNR of the received signal is lessthan a threshold, then transmitter 310 and receiver 320 can schedule andperform a beamforming training procedure. Alternatively, if the packetreception rate falls below a threshold, transmitter 310 and receiver 320can schedule and perform a beamforming training procedure. In otherembodiments, transmitter 310 and receiver 320 perform a beamformingtraining procedure on a fixed schedule.

In one embodiment, transmitter 310 and receiver 320 can generate ameasurement of the link quality during a beamforming training procedure.Then, transmitter 310 can utilize the measurement of the link quality indetermining how to modulate the different components of a video signal.For example, if the link quality is high, meaning there is a lowprobability of losing packets, then transmitter 310 can utilizerelatively high (i.e., less robust) MCS levels to modulate the differentcomponents of the video signal. On the other hand, if the link qualityis low, meaning there is a high probability of losing data, thentransmitter 320 can utilize relatively low (i.e., more robust) MCSlevels to modulate the different components of the video signal.

Turning now to FIG. 4 , diagrams of packets for use in wirelesscommunication in accordance with various embodiments are shown. Packet400 is one example of a packet which is transmitted wirelessly inaccordance with one embodiment. In one embodiment, packet 400 includesshort training field (STF) 405 and then after STF 405 is header 410 andthen payload 415. STF 405 can be utilized to specify the channelconditions (e.g., channel estimation field) and additional information.STF 405 can also be referred to as a preamble. In one embodiment,payload 415 includes a low frequency/quality component of the videostream and is modulated using MCS 1. Inter-frame space (IFS) 420 followsthe payload 415, and then STF 425 is located after IFS 420, followed byheader 430 and payload 435. In one embodiment, payload 435 is a mediumfrequency/quality component of the video stream and is modulated usingMCS 4. In one embodiment, header 430 includes a field which specifiesthe MCS, length, and other information about payload 435. Packet 400 canalso include any number of other frames, depending on the embodiment.

In another embodiment, wireless data is sent according to the formatshown in packet 440 which includes multiple payloads. For example,packet 440 includes STF 445 followed by header 450 and payload 455. Inone embodiment, payload 455 includes the low frequency/quality componentof a video stream, and payload 455 is modulated with MCS 1, as indicatedby MCS index field 450A of header 450. Packet 440 also includes header460 back-to-back with payload 455, and with payload 465 following header460. In one embodiment, payload 465 includes the mediumfrequency/quality component of a video stream, and payload 465 ismodulated with MCS 4, as indicated by MCS index field 460A of header460.

Also, header 470 is included back-to-back with payload 465, and thenpayload 475 follows header 470. In one embodiment, payload 475 includesthe high frequency/quality component of a video stream, and payload 475is modulated with MCS 7, as indicated by MCS index field 470A of header470. Packet 440 aggregates multiple payloads together and does notutilize IFS between a payload and the next header which saves bandwidth.Also, packet 440 does not utilize a STF between a payload and asubsequent header, which saves additional bandwidth. By sending packetsusing the format of packet 440 and avoiding the use of an IFS and a STFat the start of subsequent payloads, the bandwidth on the channel can beutilized more efficiently. It should be understood that packets 400 and440 are merely two examples of packet formats that can be utilized invarious embodiments. In other embodiments, other packet formats arepossible and are contemplated.

Referring now to FIG. 5 , a block diagram of one embodiment oftransmitter logic 500 is shown. Source video data 505 is received by thetransmitter, and then source video data 505 is processed by transmitterlogic 500 to generate modulated packets for transmission to a receiver(e.g., HMD 220 of FIG. 2 ). In one embodiment, source video data 505 isinitially processed by extraction unit 510. Extraction unit 510 splitssource video data 505 into multiple subset bitstreams. In variousembodiments, extraction unit 510 splits source video data 505 into Nsubset bitstreams, wherein N is representative of any integer greaterthan one, and with the value of N varying from embodiment to embodiment.In one embodiment, extraction unit 510 splits source video data 505 intothree subset bitstreams (e.g., low frequency/quality subset bitstream515A, medium frequency/quality subset bitstream 515B, highfrequency/quality subset bitstream 515N). In another embodiment,extraction unit 510 splits source video data 505 into two subsetbitstreams (e.g., a high frequency/quality subset bitstream and a lowfrequency/quality subset bitstream). In other embodiments, extractionunit 510 can split source video data 505 into other numbers of subsetbitstreams.

In one embodiment, first subset bitstream 515A corresponds to a lowquality subset bitstream. First subset bitstream 515A can also bereferred to as a low frequency subset bitstream, low bitrate subsetbitstream, or low resolution subset bitstream. The other bitstreams canalso be referred to differently by replacing the term “quality” with“frequency”, “quality”, “bitrate”, or “resolution”. In one embodiment,extraction unit 510 processes source video data 505 with a highcompression ratio to produce a low bitrate subset bitstream 515A. Then,a medium bitrate subset bitstream 515B is generated from the differenceof low bitrate subset bitstream 515A and the original source video data505 at a second lower compression ratio. Other subset bitstreams can begenerated in a similar manner.

Next, mapping unit 520 maps the different subset bitstreams 515A-N todifferent MCS levels based on table(s) 525. Table(s) 525 arerepresentative of any number and type of tables that are utilized todetermine the MCS level for the different subset bitstreams 515A-N.Examples of table(s) 525 are shown in FIG. 6 in accordance with oneembodiment. In other embodiments, other table(s) 525 can be utilized tomap the different subset bitstreams 515A-N to different MCS levels.

In one embodiment, mapping unit 520 maps first subset bitstream 515A toa low MCS level, with the low MCS level inherently having a highreliability. In one embodiment, a low MCS level is used to transportfirst subset bitstream 515A with the MCS level chosen based upon thetargeted reliability and expected bandwidth requirements of the data. Inthis embodiment, mapping unit 520 maps subset bitstreams 515B-N to MCSlevels based on compression settings which are selected to fit theavailable bandwidth in the MCS level. The MCS levels for subsetbitstreams 515B-N can be selected based upon the capacity of theestablished link to the receiver.

In one embodiment, with the different subset bitstreams 515A-N havingindependent compression settings, mapping unit 520 can map each subsetbitstream 515A-N to different MCS levels. The MCS levels can be selectedbased upon risk, resilience, quality analysis, and other factors.Maximum resilience and lowest quality is achieved with the lowest MCSlevel while minimum resilience and highest quality is achieved with thehighest MCS level. In one embodiment, the low frequency/quality firstsubset bitstream 515A will be mapped to a low quality and highresilience MCS level while the high frequency/quality Nth subsetbitstream 515N will be mapped to a high quality and low resilience MCSlevel. This allows a higher level of fallback quality to be achieved incases when the high frequency/quality Nth subset bitstream 515N is notreceived correctly by the receiver.

In one embodiment, packet generation unit 530 is configured to receivethe differently modulated subset bitstreams and combine these bitstreamsinto a single packet 535. Packet 535 can then be sent over the wirelesslink to the receiver. One example of a single packet 535 for combiningmultiple differently modulated subset bitstreams is shown as packet 440(of FIG. 4 ). Other techniques for combining multiple differentlymodulated subset bitstreams can be utilized in other embodiments. Also,in other embodiments, the differently modulated subset bitstreams can besent in separate packets rather than being combined in a single packet.

Referring now to FIG. 6 , one embodiment of tables for mappingcomponents to MCS levels based on link quality are shown. In oneembodiment, the components which are generated from a given video streamare encoded and then modulation coding scheme (MCS) levels are chosenfor the components based on the current link quality. In one embodiment,the video stream is split into multiple components based on successivecompression. In another embodiment, the video stream is split intomultiple components based on frequency information. For example, in oneembodiment, the video stream is split into a low frequency component, amedium frequency component, and a high frequency component. It should beunderstood that in other embodiments, the video stream can be split intoother numbers of components. In one embodiment, the MCS levels selectedfor the components can have a fixed relationship between each other. Forexample, the low frequency/quality component will have a relatively lowMCS, the medium frequency/quality will have a relatively average MCS,and the high frequency/quality component will have a relatively highMCS.

In one embodiment, the MCS levels of the different components are scaledbased on the link quality of the wireless link between the transmitterand the receiver. The link quality can be measured using any suitabletechniques. For example, the link quality can be measured based on areceived signal strength, a signal-to-noise ratio (SNR) of a receivedsignal, a received packet error rate, and/or other factors. In oneembodiment, the link quality is measured during a beamforming trainingprocedure. The tables 605, 610, and 615 are meant to illustrate examplesof how to determine MCS levels for modulating components based on thelink quality. In one embodiment, each individual component has adifferent table. In other embodiments, other techniques for mapping eachcomponent to a MCS level based on link quality can be utilized.

In one embodiment, table 605 is utilized to determine the MCS level forthe first component of the video stream. For example, if the linkquality is low (i.e., less than a low threshold), the first component ismodulated using MCS 1. If the link quality is mediocre (i.e., in betweenlow and high thresholds), then the first component is modulated usingMCS 3. Otherwise, if the link quality is high (i.e., greater than a highthreshold), then the first component is modulated using MCS 6. The othercomponents are mapped to MCS levels from low to high in a similarfashion as the link quality changes from low (i.e., bad) to high (i.e.,good).

It should be understood that the link quality can be partitioned intoother numbers of ranges than the three shown in tables 605, 610, and615. It should also be understood that the MCS levels shown in tables605, 610, and 615 are indicative of one particular embodiment. In otherembodiments, the different components can be mapped to other MCS levelsthan those shown in tables 605, 610, and 615.

Additionally, table 620 is shown in FIG. 6 as one example of a tablewhich is utilized to determine a given quality of service (QoS) priorityand a given retry policy for each component of the video signal. Forexample, in one embodiment, the first component will be assigned a highQoS priority and will be retried if the first component is not received.Also, in this embodiment, the second component will be assigned a mediumQoS priority and will not be retried, and the Nth component will beassigned a low QoS priority and will not be retried. In otherembodiments, other QoS priorities and retry policies can be assigned tothe different video stream components.

Turning now to FIG. 7 , one embodiment of a method 700 for splitting avideo stream into multiple components and using different modulationsfor different components is shown. For purposes of discussion, the stepsin this embodiment and those of FIG. 8-9 are shown in sequential order.However, it is noted that in various embodiments of the describedmethods, one or more of the elements described are performedconcurrently, in a different order than shown, or are omitted entirely.Other additional elements are also performed as desired. Any of thevarious systems or apparatuses described herein are configured toimplement method 700.

A transmitter splits a video stream into multiple subset bitstreamsrepresenting the video stream at different quality levels (block 705).The transmitter can be any type of computing device, with the type ofcomputing device varying according to the embodiment. In one embodiment,the transmitter renders the video stream as part of a virtual reality(VR) environment. In other embodiments, the video stream can begenerated for other environments. In one embodiment, the transmittersplits the video stream into multiple subset bitstreams using successivecompression. In another embodiment, the transmitter splits the videostream into multiple subset bitstreams based on frequency information.

Next, the transmitter modulates each subset bitstream with a differentmodulation coding scheme (MCS) (block 710). Then, the transmitter sendsthe subset bitstreams which are modulated using different MCS's to areceiver (block 715). For example, in one embodiment, a first subsetbitstream, representative of the video stream at a low quality and at alower level of detail, is sent using a robust MCS. If only the firstsubset bitstream is received by the receiver, the receiver is able toreconstruct a video frame, albeit at a low level of detail, and displaythe video frame to the user such that the video frame is understood bythe user. Accordingly, the transmitter prioritizes the first subsetbitstream and modulates the first subset bitstream using a robust MCS toincrease the likelihood that the first subset bitstream if received bythe receiver. In this embodiment, a second subset bitstream,representative of the video stream at a medium quality and at a mediumlevel of detail, is sent using a MCS of average reliability. Also inthis embodiment, a third subset bitstream, representative of the videostream at a high quality and at a high level of detail, is sent using arelatively less reliable MCS compared to the MCS's used for the othersubset bitstreams. In other embodiments, other suitable techniques formodulating the different subset bitstreams can be implemented. Afterblock 715, method 700 ends. The receiver can be any type of computingdevice. In one embodiment, the receiver is a head-mounted display (HMD).In other embodiments, the receiver can be other types of computingdevices.

Referring now to FIG. 8 , one embodiment of a method 800 for utilizingdifferent retry policies for different components of a video stream isshown. A transmitter splits a video stream into multiple components(block 805). In one embodiment, the transmitter splits the video streaminto a low quality component, a medium quality component, and a highquality component. In other embodiments, the transmitter can split thevideo stream into other numbers and types of components. The transmittermodulates each component with a different modulation coding scheme (MCS)(block 810). Then, the transmitter sends the different components to areceiver using different QoS priorities and different retry policies(block 815).

If the transmitter determines that a given component was received by thereceiver (conditional block 820, “yes” leg), then the transmitter checksthe status of the next component of the video stream (block 825). In oneembodiment, the transmitter determines that the receiver received thegiven component if the receiver acknowledged the given component. If thegiven component was not received by the receiver (conditional block 820,“no” leg), then the transmitter checks the retry policy of the givencomponent (block 830). For example, in one embodiment, a retry policycan specify that the low quality component should be retried while themedium and high quality components are not retried. In otherembodiments, other retry policies can be implemented.

If the retry policy specifies that the given component should be retried(conditional block 835, “yes” leg), then the transmitter resends thegiven component (block 840). If the given component should not beretried based on its retry policy (conditional block 835, “no” leg),then the transmitter does not resend the given component (block 845).After blocks 840 and 845, the transmitter checks the status of the nextcomponent (block 825).

Turning now to FIG. 9 , one embodiment of a method 900 for determining aMCS level for a low quality component based on the link quality isshown. A transmitter and/or a receiver generates a measurement of thelink quality of a wireless link (block 905). In one embodiment, the linkquality is measured during the implementation of one or more beamformingtraining procedures. Next, the transmitter and/or the receiverdetermines if the link quality is greater than or equal to a firstthreshold (conditional block 910). If the link quality is greater thanor equal to the first threshold, then this indicates that the linkquality is relatively high. If the link quality is greater than or equalto the first threshold (conditional block 910, “yes” leg), then thetransmitter modulates a low quality component of a video stream using afirst MCS level (block 915). In one embodiment, the first MCS level isMCS 6 (i.e., 16 QAM). In other embodiments, the first MCS level can beother levels.

Next, if the link quality is less than the first threshold (conditionalblock 910, “no” leg), then the transmitter determines if the linkquality is greater than or equal to a second threshold (conditionalblock 920). If the link quality is less than the first threshold butgreater than or equal to the second threshold, then this indicates thatthe link quality is mediocre. It is noted that the first, second, andthird thresholds are adjustable and can be reprogrammed from time totime. If the link quality is greater than or equal to the secondthreshold (conditional block 920, “yes” leg), then the transmittermodulates the low quality component using a second MCS level (block915). It is assumed for the purposes of this discussion that the secondMCS level is less than (i.e., more reliable than) the first MCS level.In one embodiment, the second MCS level is MCS 3 (i.e., QPSK). In otherembodiments, the second MCS level can be other levels.

If the link quality is less than the second threshold (conditional block920, “no” leg), then the transmitter modulates the low quality componentusing a third MCS level (block 925). If the link quality is less thanthe second threshold, then this indicates that the link quality isrelatively poor. It is assumed for the purposes of this discussion thatthe third MCS level is less than the first and second MCS levels. In oneembodiment, the third MCS level is MCS 1 (i.e., BPSK). In otherembodiments, the third MCS level can be other levels. After blocks 915,925, and 930, method 900 ends. It is noted that other similar methodscan be implemented to determine how to modulate the other componentsgenerated from the video stream. It is also noted that in otherembodiments, the link quality can be compared to other numbers ofthresholds for determining which MCS level to use when modulating agiven component of the video stream.

In various embodiments, program instructions of a software applicationare used to implement the methods and/or mechanisms described herein.For example, program instructions executable by a general or specialpurpose processor are contemplated. In various embodiments, such programinstructions can be represented by a high level programming language. Inother embodiments, the program instructions can be compiled from a highlevel programming language to a binary, intermediate, or other form.Alternatively, program instructions can be written that describe thebehavior or design of hardware. Such program instructions can berepresented by a high-level programming; language, such as C.Alternatively, a hardware design language (HDL) such as Verilog can beused.

In various embodiments, the program instructions are stored on any of avariety of non-transitory computer readable storage mediums. The storagemedium is accessible by a computing system during use to provide theprogram instructions to the computing system for program execution.Generally speaking, such a computing system includes at least one ormore memories and one or more processors configured to execute programinstructions.

It should be emphasized that the above-described embodiments are onlynon-limiting examples of implementations. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. A system comprising: a transmitter; wherein thetransmitter is configured to: split a video stream into a plurality ofsubset bitstreams, wherein each of the plurality of subset bitstreamsrepresents a different quality of the video stream with higher qualitysubset bitstreams representing enhancements to lower quality subsetbitstreams; modulate each subset bitstream of the plurality of subsetbitstreams with a different modulation coding scheme (MCS) level,wherein an MCS selected for each given subset bitstream is based atleast in part on a quality of the given subset bitstream; aggregate twoor more modulated subset bitstreams of the plurality of subsetbitstreams in a single packet for transmission via a wireless network,wherein the single packet comprises at least a first header thatidentifies a first MCS level and a second header that identifies asecond MCS level different than the first MCS level; and transmit eachmodulated subset bitstream.
 2. The system as recited in claim 1, whereinthe transmitter is further configured to: modulate a first subsetbitstream with a first MCS level of a plurality of MCS levels; andmodulate a second subset bitstream with a second MCS level, wherein thesecond MCS level is a relatively less reliable MCS level than the firstMCS level.
 3. The system as recited in claim 2, wherein: the firstsubset bitstream represents the video stream at a first quality level;and the second subset bitstream represents the video stream at a secondquality level, wherein the second quality level is a relatively higherquality than the first quality level.
 4. The system as recited in claim1, wherein decoding of a given higher quality subset bitstream requiressuccessful reception of all lower quality subset bitstreams.
 5. Thesystem as recited in claim 4, wherein the transmitter is configured to:modulate a lower frequency subset bitstream with a first MCS levelresponsive to determining a measurement of link quality is greater thanor equal to a first threshold; and modulate the lower frequency subsetbitstream with a second MCS level responsive to determining themeasurement of link quality is less than the first threshold, whereinthe first MCS level is less reliable than the second MCS level.
 6. Thesystem as recited in claim 1, wherein the single packet comprises atleast a first payload corresponding to the first header and comprisingdata coded according to a first modulation coding scheme, and a secondpayload corresponding to the second header and comprising data codedaccording to a second modulation coding scheme different than the firstmodulation coding scheme.
 7. The system as recited in claim 6, whereinthe single packet is an aggregate physical layer convergence procedure(PLCP) protocol data units (PPDU) physical layer packet.
 8. A methodcomprising: splitting a video stream into a plurality of subsetbitstreams, wherein each of the plurality of subset bitstreamsrepresents a different quality of the video stream with higher qualitysubset bitstreams representing enhancements to lower quality subsetbitstreams; modulating each subset bitstream of the plurality of subsetbitstreams with a different modulation coding scheme (MCS) level,wherein an MCS selected for each given subset bitstream is based atleast in part on a quality of the given subset bitstream; aggregatingtwo or more modulated subset bitstreams of the plurality of subsetbitstreams in a single packet for transmission via a wireless network,wherein the single packet comprises at least a first header thatidentifies a first MCS level and a second header that identifies asecond MCS level different than the first MCS level; and transmittingeach modulated subset bitstream to a receiver.
 9. The method as recitedin claim 8, further comprising: modulating a first subset bitstream witha first MCS level of a plurality of MCS levels; and modulating a secondsubset bitstream with a second MCS level, wherein the second MCS levelis a relatively less reliable MCS level than the first MCS level. 10.The method as recited in claim 9, wherein: the first subset bitstreamrepresents the video stream at a first quality level; and the secondsubset bitstream represents the video stream at a second quality level,wherein the second quality level is a relatively higher quality than thefirst quality level.
 11. The method as recited in claim 8, whereindecoding of a given higher quality subset bitstream requires successfulreception of all lower quality subset bitstreams.
 12. The method asrecited in claim 11, further comprising: modulating a lower frequencysubset bitstream with a first MCS level responsive to determining ameasurement of link quality is greater than or equal to a firstthreshold; and modulating the lower frequency subset bitstream with asecond MCS level responsive to determining the measurement of linkquality is less than the first threshold, wherein the first MCS level isless reliable than the second MCS level.
 13. The method as recited inclaim 12, further comprising modulating the lower frequency subsetbitstream with a third MCS level responsive to determining themeasurement of link quality is less than a second threshold, wherein thesecond MCS level is less reliable than the third MCS level.
 14. Themethod as recited in claim 8, wherein the single packet is an aggregatephysical layer convergence procedure (PLCP) protocol data units (PPDU)physical layer packet that comprises at least a first payloadcorresponding to the first header and comprising data coded according toa first modulation coding scheme, and a second payload corresponding tothe second header and comprising data coded according to a secondmodulation coding scheme different than the first modulation codingscheme.
 15. An apparatus comprising: a processor; a radio frequency (RF)transceiver module; wherein the apparatus is configured to: split avideo stream into a plurality of subset bitstreams, wherein each subsetbitstream of the plurality of subset bitstreams represents a differentrange of components of the video stream; modulate each subset bitstreamof the plurality of subset bitstreams with a different modulation codingscheme (MCS) level, wherein each of the plurality of subset bitstreamsrepresents a different quality of the video stream with higher qualitysubset bitstreams representing enhancements to lower quality subsetbitstreams; aggregate two or more modulated subset bitstreams of theplurality of subset bitstreams in a single packet for transmission via awireless network, wherein the single packet comprises at least a firstheader that identifies a first MCS level and a second header thatidentifies a second MCS level different than the first MCS level; andtransmit each modulated subset bitstream.
 16. The apparatus as recitedin claim 15, wherein the apparatus is further configured to: modulate afirst subset bitstream with a first MCS level of a plurality of MCSlevels; and modulate a second subset bitstream with a second MCS level,wherein the second MCS level is a relatively less reliable MCS levelthan the first MCS level.
 17. The apparatus as recited in claim 16,wherein: the first subset bitstream represents the video stream at afirst quality level; and the second subset bitstream represents thevideo stream at a second quality level, wherein the second quality levelis a relatively higher quality than the first quality level.
 18. Theapparatus as recited in claim 15, wherein decoding of a given higherquality subset bitstream requires successful reception of all lowerquality subset bitstreams.
 19. The apparatus as recited in claim 18,wherein the apparatus is configured to: modulate a lower frequencysubset bitstream with a first MCS level responsive to determining ameasurement of link quality is greater than or equal to a firstthreshold; and modulate the lower frequency subset bitstream with asecond MCS level responsive to determining the measurement of linkquality is less than the first threshold, wherein the first MCS level isless reliable than the second MCS level.
 20. The apparatus as recited inclaim 19, wherein the apparatus is configured to modulate the lowerfrequency subset bitstream with a third MCS level responsive todetermining the measurement of link quality is less than a secondthreshold, wherein the second MCS level is less reliable than the thirdMCS level.